Air cushion vehicle

ABSTRACT

An air cushion vehicle of the type wherein air at superatmospheric pressure in a plenum supports a vehicle and the vehicle is provided with an inflatable bag skirt, there being a duct extending between a blower on the one hand and both the bag skirt and the plenum on the other, the plenum containing a door which can be opened or closed to control pressure differential between the inflatable skirt and the plenum whereby the vehicle may be lifted to take-off point with the plenum door closed, and take-off can be achieved by opening of the plenum door.

United States Patent Taylor [451 May 16, 1972 54] AIR CUSHION VEHICLEFOREIGN PATENTS 0R APPLICATIONS [72] Inventor: Robert Vincent Taylor, 3Forrestall Road, 1,481,938 3/1969 Germany ..180/120 Elizabeth Downs,Australia Primary Examiner-Robert J. Spar [22] Flled 1971 Attorney-CarlR. Brown [21] App]. No.: 103,622

[57] ABSTRACT 52 U.S.Cl ..180/117, 180/127 An air cushion vehicle of thep wherein air at p 51 rm.c| ..B60v 1/06, B60v 1/16 mospheric Pressure ina plenum pp a vehide and the [53] Field of Search "130/116, 1 17 120 121122 vehicle is provided with an inflatable bag skirt, there being a180/127, 128, 129 duct extending between a blower on the one hand andboth the bag skirt and the plenum on the other, the plenum contain- 56 Rf C-ted ing a door which can be opened or closed to control pressure 1 eerences l differential between the inflatable skirt and the plenum UN ESTATES PATENTS whereby the vehicle may be lifted to take-off point withthe plenum door closed, and take-off can be achieved by opening3,237,708 3/ 1966 Strasser et a1 "180/121 of the plenum doon 3,398,8098/1968 Wood et al.. ..180/127 X 3,572,461 3/197] 11 Claims, 3 DrawingFigures Bertin 180/121 P'A'TEN'TEBMAY 16 am 3.662.852

SHEET 1 [IF 2 AIR CUSHION VEHICLE This invention relates to an aircushion vehicle of the type wherein air at superatmospheric pressure ina plenum supports a vehicle above a surface over which the vehicletravels and'the vehicle is propelled by displacement of air by an airscrew.

Air cushion vehicles of this type are commonly constructed with separateengines for the air screws and the cushion fans, and this of course addsconsiderably to the cost. Furthermore it is well known that smallengines are much less reliable than large engines, and the danger ofbreakdown is therefore much greater than if the engines were of largersize. To overcome this problem it has been proposed to utilize a singleengine with a countershaft arrangement, a differentialgear arrangement,or other power apportioning systems. However these are complicated andunwieldy and are of high cost.

. One of the objects of this invention therefore is to provide asimplified mechanical transmission wherein, if desired, a single enginecan be utilized both for the cushion fan and for an air screw forsupplying thrust for the vehicle.

The invention may in one of its forms consist of a vehicle comprisingair pressure imparting means, an inflatable bag skirt, a duct extendingbetween the air pressure imparting means on'the one hand and the skirtand the plenum on the other, a plenum door in the path of air flow tothe plenum, and door control means arranged-to control opening orclosing of the plenum door to thereby control pressure differentialbetween the inflatable skirt and the plenum. It then becomes possible tomake use of known characteristics of fans and air screws, wherein a fanconstitutes the air pressure imparting means for providing the cushionair and is arranged to be efficient at relatively low speed and the airscrew at relatively high speed, and the fan can be arranged to providesufficient air to fill the peripheral bag skirt, before the air screwefficiency is sufficient to apply any substantial thrust. Thisarrangement has the additional advantage that a vehicle can be liftedalmost to take-off point by having the plenum door closed, and takeoffcan be achieved by opening the plenum door, so that the vehicle can beretained in frictional engagement with the ground or water and ready tomove at low speed the instant that the frictional engagement is releasedby opening of the plenum door. This gives a chance to achieve smoothtake-off under most conditions. v

If the air cushion fan is of the centrifugal type, as speed increasesbeyond a given speed the efiiciency will drop, and if the plenum door ispartly closed as the efficiency drops, being opened only sufficiently toensure that the air cushion exists, then the fan will be partiallychoked and thereby avoid the high power consumption which wouldotherwise exist. Thusthe additional power available from an engine uponincrease of speed is mostly available for driving of the air screw toapply thrust.

A problem which is encountered with air cushion vehicles is the dangerof loss of air cushion upon reduction of motor speed, and in the eventof the vehicle being provided with air screw for thrust, it becomesnecessary for the minimum motor speed to be sufficient to ensure thatsome cushion remains. To achieve this the invention may include as oneof its further features dual throttle means, one of the throttle meansbeing arranged to be positioned at any one of a series of set positionscorresponding to a respective series of engine speeds, and the secondspeed control means co-operating therewith and being operable only toincrease engine speed above that fixed by the position of the firstsaidspeed control means. This then enables an operator to set the lowerlimit of engine speed at sufficient speed to ensure that air cushionwill not collapse, and any speed thereafter is available for thrust.This arrangement has the-additional advantage that the amount of lift ofthe vehicle can be limited and the vehicle can for example be arrangedto have the bag skirt on one side engage water in the event of a turnbeing required over water, by leaning of the vehicle, or in the event ofa larger vehicle, by introducing plenum air to one part only of thevehicle.

Embodiments of the invention are described-hereunder in some detail withreference to and are illustrated in the accompanying drawings, in which:I

FIG. 1 is a partly sectioned elevation of an air cushion vehicle,

FIG. 2 is a fragmentary side elevation of speed control means accordingto a first embodiment, and

FIG. 3 is a similar fragmentary side elevation of speed control meansaccording to a second embodiment.

ln-FlG. 1 an air cushion vehicle 10 is provided with a hard structurehull 11 having a cabin 12 thereon, and a peripheral bag skirt 13extending downwardly from the hull to define with a plenum wall 14 andthe surface 15 over which the vehicle travels, a plenum 16.

One of the more serious hazards associated with air cushion vehicles isthat of tuck under of the bag skirt, resulting in turn in plow-in". Somebag skirts are arranged to extend outwardly from the hard structurebefore they extend downwardly and inwardly in a continuous curve. If theleading edge of such a bag skirt encounters a large object or a steepfronted wave of water, deflection of the bag is accompanied by downwardmovement, which results in further deflection or tuck under" of theskirt, and the result is a plow-in or nose dive of the vehicle. In orderto avoid this, this embodiment makes provision for a change of shape ofthe skirt 13 towards the front by extending the upper join line 18upwardly, and further by utilizing a restraining rope 19 which preventsballooning of the skirt at the bow end of the vehicle.

The vehicle 10 is provided with the plenum wall 14 which supports theinner edge of the peripheral bag skirt 13 on all sides, the plenum wallterminating at its edges above the opening of the bag. An air duct 20exists above the plenum wall so that air from a cushion fan 21 will passover the top of the upper plenum wall and enter the air bag on allsides. The plenum wall 14 is provided with a series of louvres 23interconnected with one another and also interconnected to a plenumcontrol lever (not shown), the louvres overlapping when closed tothereby provide a plenum door so that air from the duct can flow intothe space within the peripheral bag skirt 13, thereby giving lift forthe vehicle.

A single engine 25 is arranged to drive a single shaft 26 which carrieson it the fan blades of the centrifugal cushion fan 21 for supplyingcushion air and also an air screw 27 for supplying thrust.

The engine speed control means 30 is provided with a dual control, onebeing a hand control 31 and the other being a foot pedal control 32. Thehand control 31 consists of an angled lever 37 one end of which isprovided with a latch 35 which passes over teeth 36 in a quadrant 37 andthe other end of which is coupled to the outer cover 38 of a Bowdencable. A transfer arm 39 of bell crank shape is positioned near the handcontrol lever, and one end of the transfer arm is coupled to the innercable 40 of the Bowden cable. A stop 41 limits movement of the transferarm. The other end of the transfer arm is connected by a rigid orflexible link 42 to the pedal control 32 so that the foot pedal operatesthe transfer arm. Thus the inner portion of the cable is coupled to thefoot pedal and the outer portion to the hand control arm. The other endof the inner cable 40 is connected in the usual way to the throttle ofthe engine, and the arrangement is therefore such that initial speed ofthe engine can be regulated by means of the hand control which can thenbe locked in the desired position to give minimum speed which willenable the vehicle to be lifted by the bag skirt and to be justair-home. Further speed of the engine is achieved only by control of thefoot pedal and further speed is usable for the attaining of sufficientthrust to drive the vehicle. In this embodiment the idling speed is setat about 800 rpm. for the engine and at this speed the air cushion fanwill drive sufl'lcient air into the bag skirt to lift the vehicle offthe ground. However at this speed the air screw is so inefficient thatthere is no appreciable thrust. lf the engine speed is increased to say1,500 rpm. the bag skirt will become inflated to give full clearance ofthe vehicle and although some thrust is developed by the air screw atthis speed there is not sufficient thrust to force the bag over theground surface. The air can be introduced to the plenum at this stageand the vehicle lifted just clear of the ground. However by increasingthe speed to say 2,500 r.p.m. there is ample air to lift the vehiclefrom the ground by opening of the plenum door, and the thrust of the airscrew will increase considerably. This then enables the vehicle to startmoving in a forward direction, and by careful adjustment of the plenumdoor the minimum amount of air required to keep the vehicle on cushioncan be adjusted by an operator, and this then makes available extrapower to the air screw before thrusting of the vehicle in a forwarddirection. Any increase in speed will supply power used almost entirelyfor thrust purposes, since the choking effect of the plenum door willreduce the proportion of load due to the centrifugal fan. Upon suddenrelease of the accelerator pedal however the engine speed is stillsufficient to ensure that the vehicle is lifted by the air cushion. Inthe event of the vehicle being a large vehicle, the plenum is dividedinto two portions one on each side of the vehicle by a central divisionmember and the portions have separate doors, so that the doors can bedifferentially opened upon turning. This gives an automatic bankingeffect, and particularly in the event of the vehicle passing over water,the drag of the water can be made use of as the bag skirt engages thewater.

The embodiment of FIG. 3 is substantially similar to that of FIG. 2,excepting that friction is utilized instead of the teeth 36, and that apivoted quadrant 45 replaces the transfer arm 39 and link 42 of FIG. 2.

It will be seen that the conditions of driving a motor vehicle aresomewhat simulated, in that there is a necessary co-operation on thepart of an operator between the accelerator pedal and the plenum doorcontrol, and this is somewhat analogous to the co-operation existingbetween a motor vehicle clutch and its accelerator pedal. Thus theinvention has the further advantage of providing a control whichrequires a minimum amount of tuition for an operator.

If the division of plenums is achieved with a transverse wall,manouverability is improved by, for example, reducing pressure in thefront plenum and swinging the back of the vehicle. Alternatively theplenum may be divided into four or more divided portions.

Mechanical equivalents may be employed to the elements described in theabove embodiment. For example, the quadrant 45 of FIG. 3 may be replacedby a short curved tube, for example, the outer sheath of a Bowden cable,but variations of this type will be seen to lie within the invention.

What I claim is:

1. An air cushion vehicle of the type wherein air at superatmosphericpressure in a plenum supports a vehicle above a surface over which thevehicle travels and the vehicle is propelled by displacement of air byan air screw, comprising an engine, air pressure imparting means coupledfor drive to the engine, an inflatable bag skirt, a duct extendingbetween the air pressure imparting means on the one hand and the skirtand the plenum on the other, a plenum door in the path of air flow tothe plenum, and door control means arranged to control opening orclosing of the plenum door to thereby control pressure differentialbetween the inflatable skirt and the plenum.

2. An air cushion vehicle according to claim 1 wherein a horizontallyextending plenum wall divides the plenum from the duct, the plenum wallhaving an opening therein, and the plenum door being arranged to closeor partly close the opening.

3. An air cushion vehicle according to claim 2 wherein the plenum doorcomprises a plurality of interconnected louvres.

4. An air cushion vehicle of the type wherein air at superatmosphericpressure in a plenum supports a vehicle above a surface over which thevehicle travels and the vehicle is propelled by displacement of air byan air screw, comprising a horizontally extendin wall formin the upplerwall of the plenum, a centrifugal an mounted a ove the orlzontallyextending plenum wall, an engine, drive means coupling the engine to thecentrifugal fan, an inflatable bag skirt, a duct extending between thecentrifugal fan on the one hand and the skirt and the plenum on theother, the plenum wall having an opening therein, a plenum door carriedby the plenum wall and arranged to close or partly close said opening,and door control means coupled to the door and arranged to controlopening or closing of the door to thereby in turn control pressuredifferential between the inflatable skirt and the plenum.

5. An air cushion vehicle according to claim 4 wherein the engine shaft,centrifugal fan and air screw are coupled for drive to one another.

6. An air cushion vehicle according to claim 4 wherein thecross-sectional shape of the inflatable bag skirt varies due to theposition of its outer join line with the vehicle hull being higher fromthe base of the vehicle at and near the front than at the rear.

7. An air cushion vehicle according to claim 6 further comprising arestraining rope around the front end of the inflatable bag skirtretaining the upper portion of the skirt contiguous with the vehiclehull.

8. An air cushion vehicle according to claim 4 further comprising dualengine speed control means, position retaining means engaged by one ofthe speed control means arranged to secure that said speed control meansin any one of a series of set positions corresponding to respectiveengine speeds, and interconnecting means coupling the second speedcontrol means to the first speed control means and so constructed andarranged that the second speed control means is operable only toincrease engine speed above that fixed by the position of the first saidspeed control means.

9. An air cushion vehicle according to claim 8 wherein first said speedcontrol means is a hand control lever co-operating with positionretaining means and coupled to the outer cover of a Bowden cable, whilesaid second speed control means include a foot pedal coupled to theinner cable of a Bowden cable.

10. An air cushion vehicle according to claim 8 wherein said first speedcontrol means is a hand control lever co-operating with positionretaining means and coupled to the outer cover of a Bowden cable, thesecond speed control means including a foot pedal, and a bell crank andlink coupling the inner cable of the Bowden cable to the foot pedal.

11. An air cushion vehicle according to claim 8 wherein said first speedcontrol means is a hand control lever co-operating with positionretaining means and coupled to the outer cover of a Bowden cable, andfurther comprising a foot control lever and pulley means, the innercable of the Bowden cable being secured to the foot control lever butpassing over pulley means between the foot control lever and the outercover of the cable.

1. An air cushion vehicle of the type wherein air at superatmosphericpressure in a plenum supports a vehicle above a surface over which thevehicle travels and the vehicle is propelled by displacement of air byan air screw, comprising an engine, air pressure imparting means coupledfor drive to the engine, an inflatable bag skirt, a duct extendingbetween the air pressure imparting means on the one hand and the skirtand the plenum on the other, a plenum door in the path of air flow tothe plenum, and door control means arranged to control opening orclosing of the plenum door to thereby control pressure differentialbetween the inflatable skirt and the plenum.
 2. An air cushion vehicleaccording to claim 1 wherein a horizontally extending plenum walldivides the plenum from the duct, the plenum wall having an openingtherein, and the plenum door being arranged to close or partly close theopening.
 3. An air cushion vehicle according to claim 2 wherein theplenum door comprises a plurality of interconnected louvres.
 4. An aircushion vehicle of the type wherein air at superatmospheric pressure ina plenum supports a vehicle above a surface over which the vehicletravels and the vehicle is propelled by displacement of air by an airscrew, comprising a horizontally extending wall forming the upper wallof the plenum, a centrifugal fan mounted above the horizontallyextending plenum wall, an engine, drive means coupling the engine to thecentrifugal fan, an inflatable bag skirt, a duct extending between thecentrifugal fan on the one hand and the skirt and the plenum on theother, the plenum wall having an opening therein, a plenum door carriedby the plenum wall and arranged to close or partly close said opening,and door control means coupled to the door and arranged to controlopening or closing of the door to thereby in turn control pressuredifferential between the inflatable skirt and the plenum.
 5. An aircushion vehicle according to claim 4 wherein the engine shaft,centrifugal fan and air screw are coupled for drive to one another. 6.An air cushion vehicle according to claim 4 wherein the cross-sectionalshape of the inflatable bag skirt varies due to the position of itsouter join line with the vehicle hull being higher from the base of thevehicle at and near the front than at the rear.
 7. An air cushionvehicle according to claim 6 further comprising a restraining ropearound the front end of the inflatable bag skirt retaining the upperportion of the skirt contiguous with the vehicle hull.
 8. An air cushionvehicle according to claim 4 further comprising dual engine speedcontrol means, position retaining means engaged by one of the speedcontrol means arranged to secure that said speed control means in anyone of a series of set positions corresponding to respective enginespeeds, and interconnecting means coupling the second speed controlmeans to the first speed control means and so constructed and arrangedthat the second speed control means is operable only to increase enginespeed above that fixed by the position of the first said speed controlmeans.
 9. An air cushion vehicle according to claim 8 wherein first saidspeed control means is a hand control lever co-operating with positionretaining means and coupled to the outer cover of a Bowden cable, whilesaid second speed control means include a foot pedal coupled to theinner cable of a Bowden cable.
 10. An air cushion vehicle according toclaim 8 wherein said first speed control means is a hand control leverco-operating with position retaining means and coupled to the outercover of a Bowden cable, the second speed control means including a footpedal, and a bell crank and link coupling the inner cable of the Bowdencable to the foot pedal.
 11. An air cushion vehicle according to claim 8wherein said first speed control means is a hand control leverco-operating with position retaining means and coupled to the outercover of a Bowden cable, and further comprising a foot control lever andpulley means, the inner cable of the Bowden cable being secured to thefoot control lever but passing over pulley means between the footcontrol lever and the outer cover of the cable.